Focusers for molecular resonance devices



Dec. 1, 1959 E. PANNACI ET AL 2,915,709

FOCUSERS FOR MOLECULAR RESONANCE DEVICES Filed April 11, 1958 m], u 'm mmm 46 INVENTORS,

FRIEDRICH H. REDER EDWARD PANNACI.

BY W 9/ A T TORNE X States at N.J., assignors to the United States of America as represented by the Secretary of'the Army Application April 11, 1958, Serial No. 128,024 4 Claims. (Cl. 331-94) (Granted under Title 35, US. Code-(1952), sec. 266) The invention described herein maybe manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to focusers for molecular resonance devices in which oscillations are generated during transitions to lower energy states of molecular particles.

One device of this type is known the, Maser,

In the Maser, a stream of ammonia gas is passed through a focuser which separates out the molecules of lower energy state and concentrates those of higher energy state into a beam. This beam is passed into a cavity resonator where, during transitions of the molecules to lower energy states, oscillations of characteristic frequencies, called transition frequencies are radiated. The resonator is tuned to one of these frequencies, so that the latter is sustained.

One type of focuser known as the Stark focuser, consists of a plurality of straight metal rods, evenly spaced along the circumference of a circle. Alternate rods are connected to one terminal of a source of high unidirectional potential, while the intervening rods are connected to the other terminal of said source.

The rods are usually held together in a unitary assembly by means of rings of insulating material through which the rods pass. However, when a large number of such rods are arranged around a circle of small diameter, the spacing between them becomes so small that breakdown of the insulating rings occurs because of the high potential diiference between adjacent rods.

It is a principal object of the invention to provide a focuser of such shape that breakdown of the insulating rings is less likely to occur.

In accordance with the invention, the rods are so shaped that, when assembled, they form an inclosure that is generally in the shape of a dumbbell, i.e., the ends of the inclosure are of larger diameter than the intermediate portion. The spacing between the rods is therefore greater at the extremities thereof, and by placing the insulating supports in this region, breakdown is less likely to occur.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, in which:

Figure 1 is an elevational view, partly in section and with portions broken away, showing a portion of a Maser incorporating a focuser structure built in accordance with the invention; and

Figure 2 is a section along lines 22 of Figure 1.

In the drawing, there is shown a portion of a Maser including a nozzle 10, through which a stream of ammonia gas molecules pass into a focuser structure 12, comprising an even number of circularly arranged rods, in this case eight rods 14 to 21 inclusive. As above pointed out, the focuser structure separates out the particles in the lower energy state, and focuses those in the higher energy state into a sharp beam which is passed into a cavity 22 through a restricted opening therein 24. This 2,915,109 it atented Dec. 1, 1959 '2 opening has. a diameter about equal to the internal diameter of'the circle around which the focusing rods are positioned. This opening is smaller than the internal diameter of the cavity so that it is at cut oti to frequencies generated in the cavity.- 7

Each of the rods consist of a straight portion 26 for most of its length. The, upper portion of each rod includes a portion 28 bent outwardly and a, terminal portion 30 extending upwardly and parallel to the corresponding terminal portions of the other rods. The lower rod ex- 'tremities are similarly shaped, so that the entire focuser assembly comprises a straiglit intermediateportion, and upper and lower portions which flare outwardly, whereby .the' focuser structure has the general appearance of a dumbbell. I

The, nozzle 10 extends through a plate 32 of insulating material, such as, Teflon or sapphire. The upper ends of the, focuser rods also extend into. this plate so that they are rigidly held together at the. required distance. The lower extremities of the rods are similarly supported by an insulating ring 34, of the. same material, having spaced apertures througli'whi'ch the rods extend. It will be seen that by placing the insulating reinforcing elements a the upper and lower ends, where the spacing between the rods is a maximum, adjacent rods may have a higher potential difference therebetween without danger of breakdown.

Rods 14, 16, 18 and 20 terminate at a ring-shaped metal plate 36 to which they are soldered or welded. This ring has four notches on its inner periphery, such as shown at 38, so that alternate rods 15, 17, .19 and 21 can pass through the ring without touching it. The latter rods terminate in an adjustable metal collar 40 which slides over cavity 22 and it is fastened thereto by means of a screw 42. Projections 44 and 46 on the cavity support collar 40 and limit its downward movement.

Ring 36 is connected to one terminal of a high unidirectional potential source, so that alternate rods 14, 16, 18 and 20 are polarized relative to rods 15, 17, 19 and 21 which are connected to the other terminal of said source through collar 40, which is at ground potential.

The cavity 22 extends into the lower flared-out portion of the focuser structure so that its opening is positioned substantially at the lower end of the straight portion of the focuser structure. This permits a maximum of unhindered motion of the molecules, particularly at the cavity entrance. The cavity and focuser appear as one concentric unit.

In a practical embodiment of the invention, the focuser structure was made of eight rods, each having a diameter of two millimeters and equally spaced about a circle having a diameter of 0.35 inch at the narrow intermediate portion of the focuser. The overall length of the focuser between elements 30 and 38 was 4.5 inches, and the length of the intermediate straight portion 26 of the focuser rods was 3 inches. The internal diameters of the nozzle and cavity openings were 0.25 inch and 0.35 inch, respectively. A Maser so constructed can start oscillating at a focuser potential of around 5 kilovolts.

While there has been described what is at present considered a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed in the appended claims tocover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A molecular resonance device comprising means for generating a stream of gaseous particles, a focuser assembly for concentrating and focusing into a beam those of said particles in a higher energy state, said focuser assembly comprising an even number of parallel rods equally spaced around a circle, each rod being adapted t 3 to bias at a high potential relative to its adjacent rods, the end portions of said focuser assembly being flared outwardly to provide greater spacing between said rods at said end portions, and insulating means at said end portions to tie said rods together, said generating means being located at one of said end portions, and a cavity resonator at the other of said end portions andhaving an opening into which said beam is directed; o

2. A Maser comprising a nozzle for ejecting a stream of ammonia gas molecules, a focuser assembly for concentrating and focusing into a beam those of said molecules in a higher energy state, said focuser assembly comprising an even number of parallel rods equally spaced around a circle, a source of unidirectional potential, alternate rods being conp ected to one pole of a said source and the intervening rods being connected to the opposite pole of said source, the end' portions of said focuser assembly being flared outwardly to provide greater spacing between said rods at said end portions, and means to tie said rods together comprising at least one insulating element to which said rods are attached and located in the region of said greater spacing, said nozzle being located at one of said end portions, and a cavity resonator extending into the other of said end portions and having a restricted opening into which said beam is directed.

3. In a molecular resonance system having means for "generatinfia stream of gaseous particles,aStark type focusing means comprising a plurality of spaced metallic rods disposed to inclose a cylindrical space into which said particles are directed the center portion of the rods being straight and theirend portions being bent outwardly, insulating means to suppont and electrically isolate said rods at their outwardly bent ends and a direct current energy source the terminals of which are connected to alternate rods.

4. In a molecular resonance system having means for generating a stream of gaseous particles; a Stark type focusing means comprising an even number of parallel metal rods disposed to inclose a cylindrical space thru which said particles are directed, said rods being straight for most of their length and bent outwardly at their ends, insulating members within which the outwardly bent ends of the rods are anchored in spaced relation and a source of direct current energy having its terminals connected to alternate rods.

References Cited in the file of this patent UNITED STATES PATENTS 171,707 Walker Ian. 4, 1876 

